Is this clip that you are not using still in the project, if so delete and move clip to different location on hdd.
See how that goes.
It's a music track that I am still using; I have rendered and replaced the instance I am using it as well to try to fix it. It's an "echo" of the track in brown, recurs around the playhead mark. I've recreated this instance of the timeline from scratch without it and also created a new "stripped-down" project file without any unused clips in the bin.
What if you create a new sequence, select all clips from this sequence, then copy+paste it into the new sequence? Or maybe try creating a new project and import the sequence? I wonder if we could move it around enough to shake the ghost clips.